Well, not having read GTD is the source of your confusion. Here are a few concepts that may help you.
- A task is a physical action that you want or need to accomplish.
- Projects are similar to tasks, but they take more than one physical step to complete.
- Contexts are usually places, tools, or frames of mind that are necessary to do an action. Common examples are phone, computer, errands.
- Areas of responsibility are just that, areas where you are responsible for results in your life.
So the business you run could be areas or responsibility, or they could be broken down into areas. OF is not specifically set up to handle areas of focus, though I use folders in planning mode for them.
But you would probably find it very helpful to read the book, or at least a quick synopsis such as can be found
here.
Hope that helps.